Data paths using a first signal to capture data and a second signal to output data and methods for providing data

ABSTRACT

Data paths, memories, and methods for providing data from memory are disclosed. An example read data path includes a delay path, and a clocked data register. The data path has a data propagation delay and is configured to receive data and propagate the data therethrough. The delay path is configured to receive a clock signal and provide a delayed clock signal having a delay relative to the clock signal that models the data propagation delay. The clocked data register is configured to clock in data responsive at least in part to the delayed clock signal. The clocked data register is further configured to clock out data responsive at least in part to the clock signal.

TECHNICAL FIELD

Embodiments of the invention relate generally to semiconductor memory,and more specifically, in one or more illustrated embodiments, tosemiconductor memory having a data register, the data register clockedto capture read data responsive a first signal and to output read dataresponsive a second signal.

BACKGROUND OF THE INVENTION

Integrated circuits often operate based on a system clock signal thatmay be used to synchronize operation of components of the system. Asfaster operation of the system is desired, a clock frequency of thesystem clock will typically be increased. The operability of theintegrated circuits should scale with the higher clock frequency toensure error free operation at the higher speed.

An example of a circuit that is clocked at the frequency of a systemclock is a read data path that provides data from, for example, a memoryarray to be output. FIG. 1 illustrates a read data path 100. The readdata path 100 includes a multiplexer 112 coupled to a data cacheregister (DDC) and a databus 110. The DDC is segmented into two portionsDDC0 and DDC1, each of which provides read data to a respective input ofthe multiplexer 112 in response to a clock signal CLK. The read data isprovided from the DDC to the multiplexer 112 in an interleaved manner.The multiplexer 112 is controlled by the CLK signal to switch back andforth between providing read data from DDC0 and providing read data fromDDC1 to a clocked data register 130 over the databus 110. Read data isclocked into (and out of) the clocked data register 130 responsive tothe CLK signal.

Operation of the read data path 100 is described with reference to FIG.2A. At time T0 a rising edge of the CLK signal clocks DDC0 and at timeT1, after a propagation delay of DDC0, data “A” is provided (e.g.output) from DDC0 to the multiplexer 112. A falling edge of the CLKsignal at time T2 clocks DDC1 and also controls the multiplexer 112 tocouple the input from DDC0 to the databus 110 to provide read data A tothe clocked data register 130. At time T3 read data “1” is output fromDDC1 (delay relative to the falling edge of the CLK signal caused by DDCpropagation delay) and at time T4, after a propagation delay of themultiplexer 112 and the databus 110, read data A arrives at the clockeddata register 130. The data register is clocked by the rising edge ofthe CLK signal at time T5 (i.e., the next rising edge of the CLK signalfollowing the rising edge that clocked DDC0 to release data A) tocapture (e.g. clock in) read data A. Data 1 is provided by themultiplexer 112 over the databus 110 to the clocked data register 130 inresponse to the rising edge of the CLK signal at time T5. After thepropagation delay of the multiplexer 112 and the data bus 110, data 1arrives at the clocked data register 130 at time T6 and is captured bythe falling edge of the CLK signal at time T7. Data captured by theclocked data register 130 are later output (e.g. clocked out) responsiveto the CLK signal.

FIG. 2B illustrates operation of the read data path 100 with a CLKsignal having twice the clock frequency of the CLK signal of FIG. 2A. Attime T0 a rising edge of the CLK signal clocks DDC0 and at time T2,after a propagation delay of the DDC0, data “A” is output to themultiplexer 112. Due to the higher frequency of the CLK signal, afalling edge of the CLK signal occurs at time T1 before data A isprovided to the multiplexer 112. The multiplexer 112 is controlled bythe falling edge of the CLK signal at time T2 to provide data A to itsoutput, and as a result, when data A is output by DDC0 data A isprovided by the multiplexer 112 to the databus 110. Due to thepropagation delay of the multiplexer 112 and the databus 110, data A isnot provided to the clocked data register 130 until time T5. The risingedge of the CLK signal at time T3, however, is the edge designated tolatch data A (i.e., the rising edge after the rising edge clocking DDC0)into the clocked data register 130. Consequently, unknown data on thedatabus at time T3 and not data A will be captured (e.g. latched) intothe clocked data register 130. Similarly, data 1 provided by DDC1 inresponse to the falling edge of the CLK signal at time T1 will also notbe correctly captured by the falling edge of the CLK signal at T5.

As shown by FIGS. 2A and 2B, although the read data path 100 may beoperable for a clock signal having a first frequency, it may not beoperable when the clock signal is scaled to a higher second frequency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a conventional read data path.

FIGS. 2A and 2B are timing diagrams of various signals during operationof the read data path of FIG. 1.

FIG. 3 is a block diagram of a read data path according to an embodimentof the invention.

FIG. 4 is a timing diagram of various signals during operation of theread data path of FIG. 3 according to an embodiment of the invention.

FIG. 5 is a block diagram of a read data path according to analternative embodiment of the invention.

FIG. 6 is a block diagram of a memory including a read data pathaccording to an embodiment of the invention.

DETAILED DESCRIPTION

Certain details are set forth below to provide a sufficientunderstanding of embodiments of the invention. However, it will be clearto one skilled in the art that embodiments of the invention may bepracticed without these particular details. Moreover, the particularembodiments of the present invention described herein are provided byway of example and should not be used to limit the scope of theinvention to these particular embodiments. In other instances,well-known circuits, control signals, timing protocols, and softwareoperations have not been shown in detail in order to avoid unnecessarilyobscuring the invention.

FIG. 3 illustrates a read data path 300 according to an embodiment ofthe invention. The read data path 300 includes a multiplexer 312 coupledto receive read data from a data cache register (DDC) and provide thedata to a data bus 310. The DDC is shown in FIG. 3 as being split intotwo functionally operable data cache registers DDC0 and DDC1, however,other data cache register configurations (e.g., splitting the DDC intogreater or fewer functionally operable portions) may be used as well.DDC0 and DDC1 are provided data, for example, from memory (not shown inFIG. 3). As will be explained in more detail below, the data cacheregisters DDC0 and DDC1 are operated in an interleaved fashion toprovide data to the multiplexer 312. That is, DDC0 provides data at afirst time while DDC1 is loaded with data, and DDC 1 provides data at asecond time while DDC0 is loaded with data. The read data is providedover the databus 310 to a clocked data register 330 that clocks in theread data responsive to a first clock signal and outputs read dataresponsive to a second clock signal. The clocked data register 330 isillustrated in FIG. 3 as a first-in-first-out (FIFO) register, however,other clocked registers now known or later developed may be used aswell. The read data path 300 further includes a matched delay path 320that delays an input clock signal to provide a delayed clock signal CLKdto clock read data into the clocked read register 330. The delay path320 includes a first model delay 315 that models a propagation delay ofthe DDC to provide a delayed clock signal CLKDEL. The output of themodel delay 315 may be used to control input selection of themultiplexer 312. The delay path 320 further includes a second modeldelay 322 that receives the CLKDEL signal from the first model delay 315and models a propagation delay of the multiplexer 312. The second modeldelay 322 provides the delayed clock signal CLKd to the clocked readregister 330 over a signal path that generally matches (i.e. hasapproximately the same propagation delay as) the propagation delay ofthe databus 310.

In the embodiment of the read data path 300 shown in FIG. 3, a clocksignal CLK is provided to the delay path 320 to provide the delayedclock signal CLKd to be used to clock read data into the clocked readregister 330. The CLK signal may be used to clock read data out of theclocked read register 330. As will be described in more detail below,delaying the CLK signal by approximately the same propagation delay asthe read data from the DDC and through the multiplexer 312 and over thedatabus 310, and clocking read data into the clocked read register 330with the CLKd signal may facilitate accurate capturing (e.g. latching)of read data.

FIG. 4 will be referenced to describe operation of the read data path300 with a clock signal having a frequency approximately twice that ofthe CLK signal of FIG. 2A. As previously discussed, the read data path100 of FIG. 1 was unable to accurately latch data from the DDC using aclock signal of this frequency.

In operation, at time T0 a clock transition of the CLK signal clocks theDDC0 and data “A” propagates through DDC0 to be output to themultiplexer 312 at time T2. The CLK signal is also provided to the delaypath 320, which as previously discussed, includes the first model delay315 that models a propagation delay of the DDC. This results in adelayed clock signal CLKDEL having clock transitions relative to clocktransitions of the CLK signal with approximately the same delay data Ahas relative to the CLK signal clocking the DDC. As previouslydiscussed, the CLKDEL signal may be used to control the multiplexer 312in some embodiments. For example, the CLKDEL signal may be used tocontrol which of the inputs of the multiplexer 312 is coupled to itsoutput. In the embodiment the operation of which is shown in FIG. 4, thetransition of the CLKDEL signal controls the multiplexer 312 to couplethe input receiving data A from DDC0 to its output, resulting in data Abeing output to the data register 330 after a propagation delay of themultiplexer 312 (not shown in FIG. 4).

Data A arrives at the input of the data register 330 a finite time afterbeing output from the multiplexer 312 due to a propagation delay of thedatabus 310 coupling the output of the multiplexer 312 to the dataregister 330. The CLKd signal is provided to the data register 330 bythe model delay 322 and is based on the CLKDEL signal. The CLKd signalis delayed by an amount approximately equal to the propagation delay ofthe databus 310, and is used to clock the data register 330 at time T5to capture data A. Although the rising edge of the CLKd signal at timeT5 is illustrated as coincident with Data A becoming valid, the dataregister 330 may be configured to provide a finite delay from the risingedge (or falling edge) of the CLKd signal before actually latching dataat its input to allow the data to stabilize. The CLK signal is used tolater clock data A from the read register 330 (not shown in FIG. 4).

With respect to the interleaved operation of DDC1, after time T0 andbefore time T2 a clock transition of CLK at time T1 clocks the DDC1 anddata “1” propagates from DDC1 to be output to the multiplexer 312 attime T4. The CLKDEL signal, which is delayed by the model delay 315,clocks the multiplexer 312 to couple the input receiving data 1 fromDDC1 to its output. As with data A output by the multiplexer 312, data 1is output by the multiplexer 312 in response to the clock transition ofCLKDEL at T4 and will take a finite time to propagate over the databus310 to the data register 330. As with clocking the data register 330 tocapture data A, the delayed CLKd signal having a delay approximatelyequal to the propagation delay of data 1 from the multiplexer 312 to theread register 330 is used to clock the data register 330 to capture data1. Data 1 is later clocked out of the data register 330 by the CLKsignal.

As further shown in FIG. 4, a transition of the CLK signal at time T3clocks the DDC0 and data “B” propagates through DDC0 to be provided tothe multiplexer 312 at time T6. The CLKDEL signal having approximatelythe same delay relative to the CLK signal as the data propagation delayof the DDC controls the multiplexer 312 to couple the input receivingdata B to its output responsive to the transition of the CLKDEL signalat time T6. Data B is output to the data register 330 after apropagation delay of the multiplexer 312 (not shown in FIG. 4) and iscaptured by the data register 330 at time T9 responsive to the CLKdsignal. The CLKd signal, as previously discussed, has approximately thesame propagation delay as data B over the data path. After time T3 andbefore time T6 a clock transition of CLK at time T5 clocks the DDC1 anddata “2” propagates from DDC1 to be output to the multiplexer 312 attime T8. The CLKDEL signal, which is delayed by the model delay 315 ofthe delay path 320, clocks the multiplexer 312 to couple the inputreceiving data 2 from DDC1 to its output. Data 2 is output by themultiplexer 312 in response to the clock transition of CLKDEL at T8 andwill take a finite time to propagate over the databus 310 to the dataregister 330. As with clocking the data register 330 to capture data B,the delayed CLKd signal having a delay approximately equal to thepropagation delay of data 2 over the data path 310 is used to clock thedata register 330 to capture data 2.

The operation of the read data path 300 to capture data output by theDDC in the interleaved manner continues as previously described. Insummary, the read data path 300 facilitates accurately capturing readdata into the data register 330 by delaying the clock signal used toclock data out from the DDC by a delay approximately equal to thepropagation delay of the data path (e.g., propagation delay of DDC,multiplexer 312, and databus 310) to clock data into the data register330. The read data is asynchronously loaded into the data register 330by the delayed clock signal. Moreover, the read data path 300 may allowthe datapath as a whole to be operated with a delay that is greater thana clock period of the CLK signal.

FIG. 5 illustrates a read data path 500 according to an embodiment ofthe invention. The data path 500 includes a multiplexer 512 coupled toreceive read data from a data cache register (DDC) and a databus 510 onwhich data is provided by the multiplexer 512. As with the read datapath 300 (FIG. 3), the DDC is shown in FIG. 5 as being split into twofunctionally operable data cache registers DDC0 and DDC1, however, otherdata cache register configurations may be used as well. DDC0 and DDC1are provided data, for example, from memory (not shown in FIG. 5). Thedatabus 510 provides read data to a clocked data register 530 thatclocks in read data responsive to a first clock signal and outputs readdata responsive to a second clock signal. The clocked data register 530is illustrated in FIG. 5 as a first-in-first-out (FIFO) register,however, other clocked registers now known or later developed may beused as well. The read data path 500 further includes a delay path 520that delays an input clock signal to provide a delayed clock signal. Thedelay path 520 includes a first model delay 515 that models apropagation delay of the DDC to provide a delayed clock signal CLKDEL,and further includes a second model delay 522 that receives the CLKDELsignal from the first model delay 515 and models a propagation delay ofthe multiplexer 512. The second model delay 522 provides a delayed clocksignal CLKd to the clocked data register 530 over a signal path having apropagation delay matched to the databus 510.

The read data path 500 is similar to the read data path 300 of FIG. 3,but the multiplexer 512 is controlled by a delayed clock signal CLKDMUXprovided by a delay 514 rather than a delayed version of the CLK signalprovided by the matched delay path 520. The CLKDMUX signal is based atleast in part on the CLK signal. The delay 514 may be a trimmable delayhaving a delay that can be adjusted by trimming. As with the read datapath 300, however, the CLK signal is provided to the delay path 520 toprovide a CLKd signal to the data register 530 having approximately thesame delay as the propagation delay of DDC, multiplexer 512, and thedatabus 510 to clock read data into the clocked register 530. The CLKsignal is used to clock read data out of the clocked data register 530.Operation of the read data path 500 is similar to that previouslydescribed with respect to the read data path 300 except that themultiplexer 512 switches between outputting data from DDC0 and DDC1responsive to the CLKDMUX signal.

FIG. 6 illustrates a memory 600 including a read data path according toan embodiment of the invention. The memory 600 includes an array 630 ofmemory cells arranged in banks of rows and columns. Command signals, theaddress signals and the write data signals are generally applied to thememory 600 as sets of sequential input/output (“I/O”) signals(illustrated in the example of FIG. 6 as I/O[7:0] and/or I/O[15:0])transmitted through an I/O bus 634. Similarly, read data signals areoutput from the memory 600 through the I/O bus 634. The I/O bus isconnected to an I/O control unit 640 that routes the signals between theI/O bus 634 and an internal data bus 642, an internal address bus 644,and an internal command bus 646. The memory 600 also includes a controllogic unit 65Q that receives a number of control signals eitherexternally (illustrated in the example of FIG. 6 as CE#, CLE, ALE, WE#,RE#, and WP#) or through the command bus 646 to control the operation ofthe memory 600. The address bus 644 applies row address signals to a rowdecoder 660 and column address signals to a column decoder 664.Similarly, the column decoder 664 enables write data signals to beapplied to bit lines for columns corresponding to the column addresssignals and allow read data signals to be coupled from bit lines forcolumns corresponding to the column address signals.

In response to the memory commands decoded by the control logic unit650, the memory cells in the array 630 are erased, programmed, or read.The memory array 630 is programmed on a row-by-row or page-by-pagebasis. After the row address signals have been applied to the addressbus 644, the I/O control unit 640 routes write data to a read and writeregister 680. The read and write register 680 provide the write data toa data cache register 670. The write data are stored in the data cacheregister 670 in successive sets each having a size corresponding to thewidth of the I/O bus 634. The data cache register 670 sequentiallystores the sets of write data for an entire row or page of memory cellsin the array 630. All of the stored write data are then used to programa row or page of memory cells in the array 630 selected by the rowaddress coupled through the address bus 644. In a similar manner, duringa read operation, read data from a row or page of memory cells selectedby the row address coupled through the address bus 644 are stored in thedata cache register 670. The read and write register 680 receives theread data from the data cache register 670 at a read data path 690, forexample, a read data path according to an embodiment of the invention.Sets of read data corresponding in size to the width of the I/O bus 634are then sequentially transferred through the I/O control unit 640 fromthe read and write register 680 to the I/O bus 634.

From the foregoing it will be appreciated that, although specificembodiments of the invention have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

What is claimed is:
 1. A data path, comprising: a delay path configuredto receive a clock signal and provide a delayed clock signal having adelay relative to the clock signal that is approximately the same as adata propagation delay of the data path; and a clocked data registercoupled to the delay path and configured to capture data responsive atleast in part to the delayed clock signal and further configured toprovide the data responsive at least in part to the clock signal.
 2. Theread path of claim 1, wherein the data path further comprises: amultiplexer having a plurality of inputs configured to receive the dataand further configured to selectively output the data to the clockeddata register from one of the plurality of inputs responsive at least inpart on a multiplexer control signal; and a data bus coupled to themultiplexer, the data bus having a data bus propagation delay.
 3. Thedata path of claim 2, wherein the delay path comprises: a model delayconfigured to provide a delay approximately equal to a first datapropagation delay of a data cache register from which the data isreceived by the multiplexer and a second data propagation delay of themultiplexer; and a signal path coupled to the model delay and configuredto have a propagation delay substantially equal to the data buspropagation delay.
 4. The data path of claim 3, wherein the delay pathis configured to provide a first delayed clock signal having the firstdata propagation delay, the multiplexer control signal based at least inpart on the first delayed clock signal.
 5. The data path of claim 3,wherein the delay comprises: a first model delay configured to model apropagation delay of the data cache register and a second model delayconfigured to model a propagation delay of the multiplexer.
 6. The datapath of claim 2, further comprising a data cache register coupled to themultiplexer.
 7. The data path of claim 1, wherein the clocked dataregister comprises: a FIFO register.
 8. A data path, comprising: aclocked data register configured to capture data responsive to a firstclock signal and to provide the data responsive to a second clocksignal; and a delay path coupled to the clocked data register andconfigured to receive the second clock signal and provide the firstclock signal to the clocked data register, the first clock signal havinga delay relative to the second clock signal, and wherein the first clocksignal is provided by the delay path to clock the data into the clockeddata register.
 9. The data path of claim 2, wherein the multiplexercontrol signal is based at least in part on the clock signal.
 10. Thedata path of claim 2, wherein the multiplexer control signal is providedby a trimmable delay configured to receive the second clock signal. 11.The data path of claim 8, wherein the delay path comprises: a modeldelay coupled to receive the second clock signal and configured toprovide a delay approximately equal to a data propagation delay of adata cache register coupled to receive the second clock signal.
 12. Thedata path of claim 8, wherein the data path further comprises: a datacache register coupled to receive the second clock signal and operatedin an interleaved fashion to provide data to be captured by the clockeddata register.
 13. A memory, comprising: a memory array configured tostore data; a data cache register coupled to the memory array andconfigured to receive the data from the memory array; a delay pathcoupled to the data cache register and configured to receive a clocksignal and provide a delayed clock signal having a delay relative to theclock signal that is approximately equal to a propagation delay; and aclocked data register coupled to the delay path and configured tocapture the data responsive at least in part to the delayed clock signaland further configured to provide the data responsive at least in partto the clock signal.
 14. A method for providing data from memory,comprising: providing the data from a data cache register to a FIFOregister responsive to a first clock signal; loading the data into theFIFO register asynchronously responsive to a second clock signal havinga delay relative to the first clock signal; and providing the data fromthe FIFO register synchronously responsive to the first clock signal.15. The method of claim 14, wherein providing data from a data cacheregister comprises providing the data from the data cache register in aninterleaved manner.
 16. The method of claim 15, further comprisingcontrolling a multiplexer coupled to the data cache register responsiveto a delayed clock signal, the delayed clock signal based at least inpart on the first clock signal.
 17. The method of claim 14, wherein thedelay is substantially equal to a propagation delay of the data from thedata cache register to the FIFO register.
 18. A method for providingdata from memory, comprising: loading a FIFO register with the dataresponsive at least in part to a first clock signal, the data providedfrom a data cache register to the FIFO register, the first clock signalhaving a delay relative to a second clock signal approximately equal toa data propagation delay from the data cache register to the FIFOregister; and providing the data from the FIFO register and providingthe data from the data cache register responsive at least in part to thesecond clock signal.
 19. The method of claim 18, further comprisinginterleaving the providing of data from the data cache register.
 20. Themethod of claim 18, further comprising delaying the second clock signalthrough a delay path to provide the first signal.
 21. The method ofclaim 20, wherein the data propagation delay from the data cacheregister to the FIFO register includes a propagation delay of a data buscoupled to the FIFO register.